Exposure to ultra violet radiation can cause a wide range of deleterious effects in human skin, including dehydration, burning, premature aging, and discolouration. In addition, it has been widely accepted and documented that excessive exposure to ultraviolet radiation can be carcinogenic in humans. Exposure to ultraviolet radiation is of a particular concern for individuals that spend a significant amount of time outside and exposed to the sun, and those having fair completions and who are less tolerant to the sun's ultraviolet rays. In addition, damage to the earth's ozone layer and its ability to filter out ultraviolet radiation has further raised the concern over the harmful effects that exposure to ultraviolet radiation may have.
For the above reasons a variety of different devices and skin preparations have been developed in order to limit exposure to solar radiation. So called "sunscreen" clothing has been developed that filters or blocks ultraviolet radiation. In addition, significant advances have been made in the development and commercialization of topical sunscreen preparations that may be applied to the skin in order to provide protection from ultraviolet rays.
While sunscreen preparations are, to varying degrees, reasonably effective in filtering out harmful radiation and limiting the skin's exposure to the sun, they are limited with respect to their duration of usefulness, and in many cases may also be worn away through physical activity, bathing or swimming activities. As a result, sunscreens must typically be re-applied on a regular basis, the frequency of which may increase depending upon the physical activity of an individual. In some situations, individuals are engaged in activities that prevent them from re-applying sunscreen on a regular basis. In other cases individuals merely forget to apply or re-apply sunscreen. In yet other situations, an individual may inappropriately gauge the level of sunscreen preparation necessary at any particular time of the day, or on any day. That is, commercially available sunscreen preparations are rated on what is commonly referred to as a sunscreen protection factor (SPF) scale. Generally the higher the SPF factor the greater the sunscreen protection that is provided. However, often individuals are unaware of the intensity of the sun's rays during a particular time of day, or with changing weather conditions, and fail to apply sunscreen having an adequate SPF factor. The natural characteristics of the skin of different individuals and the rate at which different individuals perspire will result in the effectiveness of sunscreens varying dramatically for different people. Finally, it is often not appreciated by individuals that ultraviolet radiation can cause degradation of a sunscreen preparation requiring further application regardless of perspiration, swimming or physical activity.
There is therefore a need for a device that is capable of indicating when an individual has been exposed to ultraviolet radiation and the level of ultraviolet radiation exposure. Such a device would allow an individual to know when exposure to sunlight should be terminated or when further sunscreen preparations should be applied.